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Integrating foliar zinc (Zn) application into common practices, e.g. application of pesticides, phosphorus (P) or biostimulants, is a feasible agronomic strategy of wheat biofortification. However, it remains unclear how this integrated approach affects the efficacy of foliar Zn sprays, especially under unfavourable environmental conditions. Here, two field experiments considering Zn forms (ZnSO4 and zinc-glycine) and applications (alone or combined with pesticides, KH2PO4, and biostimulants amino acids or fulvic acids) were conducted in two seasons (2017 and 2018), and their effects on the magnitude of grain Zn increment and bioavailability were evaluated. The results showed that less precipitation in 2018 caused 11.7–52.2% yield losses than in 2017, which increased grain Zn concentration by 13.4–58.4%. Foliar application of Zn-glycine did not surpass ZnSO4 spray in regarding to grain Zn concentration and bioavailability. Grain Zn concentration substantially decreased in plants sprayed with KH2PO4 irrespective of Zn forms applied, indicating strong antagonistic effects of P supply on grain Zn enrichment. There were no differences in grain Zn density between the applications of amino acids and fulvic acids. However, grain Zn bioavailability significantly increased by 22.3 and 23.4% in the Zn plus pesticides treatment when sprayed with fulvic acids in 2017 and with amino acids in 2018, respectively. Overall, environmental conditions and foliar Zn management considering Zn forms and applications accounted for 35–45% and 20–37% of explained variation in the magnitude of grain Zn increment, respectively. The results demonstrated that management and environment are crucial factors to consider in agronomic biofortification of wheat.

Combined foliar application of zinc sulphate (ZnSO4) and selenium (Se) has been practiced in wheat biofortification. However, it remains elusive that whether the combined application affects Zn and Se distribution to grain, the efficacy of biofortification and bioavailability in wheat, due to the accompanying sulphate sources. Selenite and ZnSO4 were applied either alone or simultaneously to foliage of wheat in field, and their impacts on Zn and Se partitioning in plants, enrichment and bioavailability in whole grain, bran and flour, as well as amino acid profile in flour, were closely investigated. Grain yield was not influenced by any of the foliar Zn and Se applications. Grain Zn and Se concentrations reached 58.3–77.9 and 0.30–0.74 mg kg−1 in Zn‐ and Se‐sprayed plants, respectively, and the estimated daily‐absorbed Zn by a reference adult from grain and flour were enhanced by 1.2‐ to 2.4‐fold than the control, as well as 16.8‐fold increase on average for daily Se intake. Combined Zn and Se application led to a 32%–37% reduction in Se concentrations and daily Se intake of whole grain and flour in one of the two seasons when compared with the foliar Se spray alone, which was partly associated with the reduced Se distribution to grains. Alternatively, similar responsive patterns of methionine and cysteine with grain and flour Se concentrations further suggested that zinc sulphate and selenium interactions in Se accumulation act through the metabolism of sulphur‐containing amino acids in wheat plants. Further, the substantial Zn enrichment in flour paralleled to the increase of amino acid profiles such as aspartate, glutamate, glycine and lysine, but not to the total amino acid content. Overall, wheat was successfully biofortified with Zn and Se through combined foliar applications, although an antagonistic impact of ZnSO4 spray on the magnitude of Se biofortification occurred in some cases.

Soil organic carbon (SOC) is essential for soil fertility and climate change mitigation, and carbon can be sequestered in soil through proper soil management, including straw return. However, results of studies of long-term straw return on SOC are contradictory and increasing SOC stocks in upland soils is challenging. This study of North China upland agricultural fields quantified the effects of several fertilizer and straw return treatments on SOC storage changes and crop yields, considering different cropping duration periods, soil types, and cropping systems to establish the relationships of SOC sequestration rates with initial SOC stocks and annual straw C inputs. Our meta-analysis using long-term field experiments showed that SOC stock responses to straw return were greater than that of mineral fertilizers alone. Black soils with higher initial SOC stocks also had lower SOC stock increases than did soils with lower initial SOC stocks (fluvo-aquic and loessial soils) following applications of nitrogen-phosphorous-potassium (NPK) fertilizer and NPK+S (straw). Soil C stocks under the NPK and NPK+S treatments increased in the more-than-20-year duration period, while significant SOC stock increases in the NP and NP+S treatment groups were limited to the 11- to 20-year period. Annual crop productivity was higher in double-cropped wheat and maize under all fertilization treatments, including control (no fertilization), than in the single-crop systems (wheat or maize). Also, the annual soil sequestration rates and annual straw C inputs of the treatments with straw return (NP+S and NPK+S) were significantly positively related. Moreover, initial SOC stocks and SOC sequestration rates of those treatments were highly negatively correlated. Thus, long-term straw return integrated with mineral fertilization in upland wheat and maize croplands leads to increased crop yields and SOC stocks. However, those effects of straw return are highly dependent on fertilizer management, cropping system, soil type, duration period, and the initial SOC content.

Increasing soil organic carbon (SOC) is a widely accepted strategy to offset greenhouse gases and improve soil quality. Straw return can modify SOC dynamics and increase its stock, which are also i...

Given energy and water scarcity, it is necessary to develop an in-depth understanding of the energy-water nexus in China for its sustainable development. Previous studies have focused on nexus accounting, synergy conservation, and system optimization, but its induction mechanism along the supply chains has not been uncovered. This paper proposes a top-down structural path analysis (SPA) and combines it with an environmental input-output model (EIOM) to identify the critical final demand, consumption sectors, and supply chain paths inducing the energy-water nexus. The results show that the largest final demand of water for energy production (WFE) is capital formation, while the largest final demand of energy for water supply (EFW) is urban consumption. The distribution of WFE at different production layers shows an inverted U shape. Most WFE is indirectly consumed by other sectors, such as construction, through three-step supply chain paths. In contrast, the distribution of EFW shows a L shape, and most EFW is directly consumed by the final demand. In addition, some critical supply chain paths inducing more WFE and EFW are identified. Finally, some policies targeting the energy-water nexus management are proposed, which are conducive to resource conservation and the sustainable supply of energy and water.

To identify the interaction pattern features and driving forces of intersectoral CO2 emissions, this paper studies the interaction pattern types, interaction linkage strengths and key interaction patterns of 28-sector CO2 emissions flow networks in China from 1997 to 2015 via network motif analysis. Network motif analysis is a useful tool for measuring interactions between agents and their function in networks. This paper extends network motif analysis by investigating the weighted edges of motifs to observe the function of motifs. The results show that in 1997–2002 and 2008–2015, the strongest carbon intensity sectors, including electricity production, metal smelting and gas production, were the greatest contributors to the increase in intersectoral CO2 emissions. From 2003 to 2007, the strongest energy intensity sectors, including electricity production and fuel processing, were the greatest contributors. In contrast, the strongest export intensity sectors, including other electronic equipment, leather manufacturing, instrumentation, and textile, were the largest contributors to the decrease in intersectoral CO2 emissions. Second, the strongest interaction linkages were between construction and nonmetallic products and metal smelting, machinery and construction and metal smelting, construction and nonmetallic products, construction and metal smelting. Third, the key interaction patterns for the increase in intersectoral CO2 emissions were patterns such as infrastructure-export, manufacturing intensive, energy consumption, and energy tracing, while the export-intensive pattern and high export pattern were the key interaction patterns for the decrease in intersectoral CO2 emissions. This paper is beneficial to the establishment of a coordinated emissions reduction mechanism across sectors.

Knowledge about the changes in soil organic carbon (SOC) stocks and grain yields under different tillage and straw management is necessary to assess the feasibility and sustainability of conservation agriculture. An 8-year experiment was conducted in an intensive wheat (Triticum aestivum L.)–maize (Zea mays L.) rotation system in the southern Loess Plateau of China. Three tillage methods [control with no-tillage and straw removal (CK), no-tillage with straw stubbles 30–40 cm in height (NT), and rotary tillage with straw incorporation (RT)] were applied before maize planting, and two straw treatments [straw return (SR) and no straw return (SR0)] were applied after maize harvest. Thus, the treatments included CK-SR, CK-SR0, NT-SR, NT-SR0, RT-SR, and RT-SR0. Over 8 years, the SOC stock exhibited similar dynamic trends in all treatments, but was higher in NT, RT, and SR plots than in CK-SR0 plots. Compared with the initial soil, the SOC stock increased largest (34.1%) in NT-SR. Compared with the CK-SR0, the NT-SR, RT-SR, CK-SR, NT-SR0 and RT-SR0 increased the wheat grain yield by 47.2%, 36.8%, 24.9%, 25.1%, and 20.0%, respectively. The NT, RT and SR increased crop yield stability with the highest sustainable yield index in NT-SR for both wheat (0.67) and maize (0.70). This study showed the NT-SR was the best strategy for improving SOC stocks, grain yields and agricultural sustainability for the wheat-maize rotation system in northwestern China and other areas with similar climates and cropping systems.

Sectors tend to generate pressure on the environment due to its large amounts of emissions. The aim of this study is to identify critical betweenness sectors and transactions that play an important intermediate role in the supply chain, which can provide additional insights for CO2 emissions. Based on the input-output and energy consumption data in China, the notion of network centrality and structural path analysis method are employed in this paper to identify critical betweenness sectors and transactions, and then the evolutionary trends of betweenness sectors and transactions are analyzed from 2005 to 2015. The results show that some critical betweenness sectors, such as Metal products sector and Electrical equipment sector, have huge potential for carbon emission reduction, which fail to receive sufficient attention from the perspective of production or consumption. Some critical transactions, such as the transaction from Nonmetal products sector to Construction sector, have a large amount of CO2 emissions. The transaction from Metallurgy sector to Electrical equipment sector became increasingly important in China from 2005 to 2015. Additionally, the evolutionary trends of different transactions are significantly different. The findings reveal that special attention should be paid to these critical betweenness sectors and transactions and policy development should be dynamic to respond to changes in CO2 emissions that are generated by different betweenness sectors and transactions.

As the largest carbon emitter, China is facing huge pressure and has a heavy task to control emissions. Previous studies have mainly focused on the production- and consumption-based sectors with large emissions, but few draw the whole picture of emission flows in Chinese supply chains in which direct carbon emissions (DCE) become embodied carbon emissions (ECE).This study aims to combine input-output model and structural path analysis to trace carbon emission flows from primary producer sectors to final consumer sectors based on the data of China in 2012. The results show that the total carbon emissions were 9208.33 Mt, and capital formation was the main final demand with the share of 44.22%. Production and Supply of Electricity released the largest DCE, and Construction was responsible for the largest ECE. Nearly 90% of emissions occurred in upstream sectors of the supply chains, Manufacturing and Electricity/Gas/Water are the important transfer sectors. The distribution of DCE and ECE of different sectors have different patterns. Electricity/Gas/Water released most of its DCE for its two-step downstream sectors (22.64%). Construction got more ECE indirectly from its one-step upstream sectors (29%) and two-step upstream sectors (26%). Controlling inputs from upstream or outputs to downstream can help to develop more effective measures to reduce emissions, especially for achieving the reduction target of one certain sector. Furthermore, some supply chain paths with more emissions, such as “Metal Smelting→ Construction→ Capital formation”, should be paid more attention. Reducing intermediate purchases or using cleaner alternatives can stimulate sectors along the supply chains to control emissions together and construct green supply chains.

The indirect carbon emission embodied in the intermediate input is also an important indicator of assessing a producer’s carbon emissions. Structural analysis of indirect carbon emissions is helpful to understand the responsibilities between producers and pay efforts to key areas. The aim of this study is to analyze indirect carbon emissions embodied in intermediate input between sectors and explore the distribution structure of indirect carbon emissions flow network (namely, ICEFN). Based on the modified input-output model and complex network theory, this study constructed four directed and weighted ICEFNs with 28 sectors from 1997 to 2012. The results show that indirect carbon emissions between sectors are significantly higher than direct carbon emissions, accounting for nearly 70% of the total carbon emissions of China. Second, we analyzed the embodied carbon emission intensity (namely, ECI) of each sector. Although the ECI has been decreasing over time, the decrease has increasingly diminished, which indicates that the additional carbon emission reductions are more difficult. Third, we identified the key sectors which play different roles in the ICEFNs. Meanwhile, we studied the key paths which show more closed relationships between some sectors in ICEFNs. Finally, based on the above analysis, we made policy recommendations.

We quantified the effects of different straw return modes on soil organic carbon (SOC), total nitrogen content (TN) and C:N ratios in a wheat/maize double‐cropping agricultural system by analysing their content in different soil aggregate sizes and density fractions under four modes of straw return: (a) no return/retention of wheat and maize straw (Control); (b) retention of long wheat stubble only (Wheat Stubble); (c) retention of long wheat stubble and return of chopped maize straw (Mixed); and (d) return of chopped wheat and maize straw (Both Chopped). The Mixed and Both Chopped straw return modes produced the highest crop yields. Relative to the Control, SOC stock was 9.6% greater with the Mixed treatment and 14.5% greater with the Both Chopped treatment, whereas the Wheat Stubble treatment had no effect on SOC. Mixed and Both Chopped significantly enhanced TN stock relative to the Wheat Stubble and Control treatments. Compared with the Control, the Mixed and Both Chopped treatments increased the mass proportions of large macroaggregates and reduced the silt plus clay fraction; Mixed and Both Chopped caused a significant increase in SOC and TN in large and small macroaggregates; the Mixed treatment significantly increased SOC content in the coarse and fine intra‐aggregate particulate organic matter (iPOM) density fractions of large macroaggregates, whereas Both Chopped increased SOC in the coarse iPOM, fine iPOM and mineral‐associated organic matter (mSOM) density fractions of both large and small macroaggregates; and Mixed and Both Chopped enhanced TN content in coarse iPOM and fine iPOM within small macroaggregates. Although the Mixed treatment was slightly less effective at improving C sequestration in agricultural fields than the Both Chopped treatment, the Mixed treatment may nonetheless be the optimal plant residue management mode in terms of minimizing time and labour due to its ability to improve soil structure, maintain organic carbon levels and provide a means of sustainable crop production in intensive wheat/maize double‐cropping systems.

The coordinated relationship between the environment, resources and economy is necessary for global sustainable development. As the basis of many countries’ economies, the steel industry has received much attention. Considering the three typical stages in the steel life cycle of ore mining, crude steel production and scrap recycling, this study aims to identify the current unbalanced relationship between environmental impacts, resource flows and economic benefits. To that end, life cycle assessment (LCA) is conducted to analyze 18 trade routes involving 8 major steel trading countries, a sustainability evaluation model is constructed containing three indicators at different levels, and the coupling coordinated degree in the steel trade routes under four scenarios is simulated and discussed. The results show that, first, the category of ecotoxicity has the greatest impact on the environment during the whole steel life cycle. Second, inequalities in trade routes are common. The Australia-Russia-US, Australia-Russia-UK, and Brazil-China-Japan routes have obvious disadvantages in terms of the resource-environment, economy-resource, and environment-economy relationships, respectively, for reasons related to yield and production technology. Third, the Australia-Russia-US route has the highest coupling coordinated degree, while the Brazil-Russia-Japan route has the lowest, thereby representing the most significant imbalanced relationship. When the development of the environment-resource relationship is improved, the imbalance of most trade routes improves significantly. When development of the economy-environment relationship increases, the improvement in coordination is mainly related to the trade routes associated with Brazil and China. With the development of the economy-resource relationship, trade routes, including those involving Russia and UK, improve significantly. Based on the above findings, this paper proposes some policy recommendations to address the imbalances of trade routes in terms of environmental impact, evaluation indicators at various levels, and coupling coordination. These suggestions can help countries and related enterprises promote the circular economy and promote the sustainable development of the steel industry chain.

Straw return is widely applied in China to achieve sustainable grain production. However, inappropriate farm practices can increase greenhouse gas (GHG) emissions and reduce soil organic carbon (SOC) sequestration, thereby increasing the carbon footprint (CFP) and affecting soil fertility and climate change. A 10-year experiment was conducted to evaluate and quantify the effects of straw management on SOC, crop yield, and CFP under a winter wheat–summer maize rotation in the Guanzhong Plain. The experiment involved seven straw-return modes, namely high wheat stubble retention and chopped maize straw return (WH-MC), high wheat stubble retention and chopped maize straw return with sub-soiling every two years (WH-MM), high wheat stubble retention and no maize straw return (WH-MN), both chopped wheat and maize straw return (WC-MC), chopped wheat and maize straw return with sub-soiling every two years (WC-MM), chopped wheat straw return and no maize straw return (WC-MN), and a control with no return of either wheat or maize straw (WN-MN). The results indicate that SOC change, crop yield, and CFP were significantly influenced by the straw-return mode in the annual wheat–maize season. SOC sequestration rate was positively correlated with cumulative plant-derived C input, which ranged from 29.4 Mg C ha −1 in WN-MN to 100.7 Mg C ha −1 in WH-MC. Of all the studied treatments, WH-MC produced the highest grain yield and lowest CFP, which were 26% higher and 20.5% lower than those of the control, respectively. However, crop yield and CFP in the individual wheat or maize seasons were only slightly affected by straw-return mode; only WC-MN in the wheat season and WH-MC, WH-MM, and WC-MN in the maize season produced a significantly higher grain yield and lower CFP compared to the no straw return treatment. Annual GHG emissions were highest in the WC-MM treatment and lowest in WH-MN. Therefore, WH-MC found to be the most suitable straw-return for lowering CFP and enhancing crop yield and SOC sequestration. However, to achieve the coordinated development of agriculture and the livestock industry it is necessary to remove some straw for animal feed and fuel, so WH-MN produced optimum yield and maintained SOC stock with low GHG emissions.

In the rapid process of globalization, merchandise trade has increased year by year, and the circulation and consumption of the energy embodied in the merchandise trade have increased. To study the relevant nature of the global embodied energy trade network (GEETN) from an overall perspective and the control and dependence relationships between various countries and regions from a partial perspective, this paper establishes a GEETN model, through an ecological network analysis (ENA) method and the motif of complex networks for research. From an overall perspective, a GEETN is a system that achieves stability quickly. Some developed countries, such as the United States and the European Union, and some emerging economies, such as China and Russia, play important roles in GEETN. From a partial perspective, in the GEETN model, US is mainly controlled by Asian countries and CA (Canada), EU is mainly controlled by other European countries, both due to their industrial layout in some extent. The scientific value of this article not only includes the improvement of model, but also provides a new perspective and a reference for the formulation of energy and climate change policies.

BRICS nations, as a representative of emerging economies, have rapid economic growth and frequent trade activities, which result in a large amount of embodied energy flow (the embodied energy of BRICS accounts for about 42.3% of the global embodied energy) in the BRICS and all over the world. This article uses multilayer network model to study the embodied energy of the BRICS. By using the weighted degree and betweenness centrality indicators, key sectors and key paths are identified. The results show that the embodied energy circulation in BRICS is still dominated by industry and natural resources sectors, such as Petroleum, Chemical and Non-Metallic Mineral Products sector. The analysis of the key paths allows us to understand Russia and South Africa are exporters of embodied energy, China is an intermediate transmission country, and India and Brazil are importers. The roles of the five countries are different, and they need to perform their own duties, cooperate with collaborative governance, to achieve energy-saving, environmentally-friendly, and efficient development of the BRICS.

Most of the previous researches estimate influencing factors impact on air quality average without considering the heterogeneity of influential factors on different levels of air quality. In order to detect the different effects of influencing factors on air quality index (AQI) between lower-AQI and higher-AQI cities, this study applies a spatial quantile regression model (SQRM) to investigate heterogeneity of influential factors on AQI, while accounting for spatial autocorrelation of AQI. The results show that heterogeneity effects of windspeed, terrain slope, urbanization sprawl and spatial autocorrelation on AQI are large across the entire AQI spectrum, while heterogeneity effects of precipitation, temperature, relative humidity, terrain fluctuation and urbanization intensity on AQI are not obvious. The spatial positive autocorrelation of AQI in higher-AQI cities is greater than that in lower-AQI cities. Compared with higher-AQI cities, the negative impact of terrain slope on AQI is lager in lower-AQI cities. One unit increase in wind speed contributes AQI to decrease 9.31 to 5.64 then to 5.39 for lower, medium and higher-AQI cities. One unit increase in urbanization sprawl would lead AQI increase 25.6 to 15.6 then to 10.5 for lower, medium and higher-AQI cities. The heterogeneity analysis of meteorological, topographic and socioeconomic factors effects on air quality are of guiding significance for realizing the differentiation of policy measures for air pollution prevention and control.

Crop straw return into arable land is a common method of disposing of excess straw in China and can improve soil dissolved organic matter (DOM) that is known to modify soil zinc (Zn) extractability and mobility. We conducted a soil box (internal dimensions, 160 × 140 × 80 mm3) experiment to evaluate the response of Zn extractability and transfer by diffusion to DOM after maize straw amendment (St, 0 and 15 g kg−1) in calcareous soil treated with ZnSO4·7H2O (Zn, 0 and 20 mg kg−1). Soil treated with St0Zn0 (control), St15Zn0, St0Zn20, or St15Zn20 was isolated in the 10-mm center of the box, and untreated soil was placed in compartments at either side. Results revealed that addition of St0Zn20 or St15Zn20 increased the concentration of Zn extracted with diethylenetriaminepentaacetic acid (DTPA-extractable Zn) in the central layer compared with control or addition of St15Zn0. Over the course of 45 days, transfer of DTPA-extractable Zn into the adjacent untreated soil was detected at 15–20 mm in soil with St15Zn20 but at 10–15 mm with St0Zn20 and only 0–5 mm with St15Zn0. Additionally, a higher amount of DTPA-extractable Zn transfer into the adjacent untreated soil also occurred in St15Zn20. This increased DTPA-extractable Zn transfer may be associated with the formation of Zn-fulvic acid complexes with the provision of DOM derived from straw. Soluble Zn combined with straw return may be a promising strategy for improving both Zn mobility and extractability in calcareous soil.

Crop residue is a commonly used organic soil amendment in summer maize (June–October)–winter wheat (October–June of next year) rotation systems. However, the effects of different straw return modes on soil aggregation and soil organic carbon (SOC) stocks in different water-stable aggregates have not been extensively investigated in these cropping systems. The objective of this study was to quantify the long-term (7 yr) impact of C input on the SOC content of four soil aggregate size classes (large macroaggregates; small macroaggregates; microaggregates, silt plus clay fraction) and in explicit SOC fractions (free light fraction, free LF; intra-aggregate particulate organic matter, iPOM; mineral-associated matter, mSOM) within the top 40 cm of soil in a wheat–maize double cropping system in Northwest China. Four treatments were examined: (i) no return (control); (ii) return of wheat straw only (WR); (iii) return of maize straw only (MR); and (iV) return of both maize and wheat straw (MR-WR). Over the experimental period, the change in SOC under the four treatments ranged from −0.96 to 5.83 Mg ha −1 and a significant linear relationship between SOC change and cumulative C input (R 2 = 0.9882, P fine iPOM > coarse iPOM > free LF. Straw return significantly increased the C stock in iPOM and mSOM relative to the control. Coarse iPOM was the most sensitive indicator of C change and mSOM was the main form of SOC under long-term straw return. A significant linear relationship existed between cumulative C input and the mass proportion of macroaggregates as well as the C content of SOC fractions (or aggregate fractions). Soil depth had a significant influence on almost all measurements, with greater values observed in the 0–20 cm layer than in the 20–40 cm layer. Overall, return of both maize and wheat straw was the best strategy for improving soil structure, soil organic carbon, and crop yield. However, straw return from one crop was sufficient to maintain initial SOC levels, and conserved straw could be used for cellulosic feedstocks.

Organic amendments are widely used to both manage soil organic C (SOC) and improve soil fertility in agro-ecosystems. However, crop production and the mechanisms of SOC sequestration following organic amendment may be affected by long-term differential N fertilizations, hence driving the dynamics in SOC fractions in cultivated fields. Our 3-yr (2016–2019) field experiment evaluated the responses of SOC sequestration and SOC fractions to organic amendments in soils with long-term contrasting N applications in a winter wheat monoculture system. We compared wheat straw return (St) and farmyard manure application (Fm) in soils with either long-term (2002–2019) N absence (-N) or normal N application (+N). Both St and Fm increased SOC stocks in the 0–20-cm layer, but Fm increased it more than St did. However, St exhibited a greater SOC sequestration rate in +N soils than that in –N soils, whereas Fm exhibited both a lower SOC sequestration rate and efficiency in +N soils than in –N soils. SOC increased across all fractions in all soils after both St and Fm. However, compared with –N soils, +N soils exhibited a lower SOC increase, specifically in the very labile fraction after St, but in the non-labile fraction after Fm. St, Fm, and +N all increased the soil C management index (CMI), but only +N increased wheat yield and its sustainable yield index (SYI). Those relationships indicated that both straw and manure amendments were responsible for both SOC sequestration and increasing the CMI, and N input was fundamentally responsible for an increased SYI and associated plant-C input. Consequently, straw return was expected to be more effective at sequestering SOC when applied to soil having had adequate long-term N application, whereas farmyard manure application was likely more effective when applied in N-deficient soil. Our field study findings provide empirical evidence that soil N availability affects SOC sequestration capacities following organic amendments, and that impacts strategies aimed at further increasing soil fertility improvements via organic amendment, especially considering that different agro-ecosystems are subject to different fertilization regimes.

Nickel, cobalt, and lithium are the most critical raw materials for lithium-ion batteries (LIBs). The increasing demand for these materials has triggered worries about the trade dependency on raw materials. Traditional trade dependency measures make it difficult to identify high-risk countries (regions) from a systematic perspective. This paper proposes a global dependency index to recalculate systemic risks in the trade dependency network. Unlike the traditional trade network analysis, we construct the resource-dependent network by taking the dependency relationship as the edge and the global dependency index as the weight. We use the new network to explore the characteristics of the overall pattern of global trade and the concentration of dependency. Then, considering the heterogeneity of trading agents, country (regional) dependency is analyzed at the local and global levels. The dependency relationship coordinates are constructed to identify high-risk countries (regions). The results show that the trade is highly concentrated. Developed and emerging economies tend to import in quantity. The absolute dependency and global dependency of agents are heterogeneous. The distribution characteristics of agent relationships in the trade dependency coordinates are apparent. According to the results, policymakers and market participants can tailor trade strategies to reduce risks. This accounting method provides ideas for future studies on trade dependency on other resources.

With international trade, energy embodied in goods flows between sectors at a global scale and forms a complex network. Using the world input-output tables from 1995 to 2009, this study aims to apply complex network theory to study the evolutionary features of global embodied energy flow between sectors. The results show that 80% of flows are between different countries, while 80% of embodied energy is consumed in the national production process. Over time, embodied energy consumption increases, and sectors tend to import more energy from sectors in other countries. The network is sensitive; change in some sector or flow can quickly spread and impact the whole system. Only 0.02% of key flows possess large amounts of embodied energy and account for 80% of embodied energy. Sectors with large-scale impact, strong impact, strong intermediary ability, and strong central ability play key roles in the network. Furthermore, the network presents an obvious clustering feature. More than 60% of sectors cluster into the top 3 largest communities, and sectors in EU countries cluster into the biggest community and attract more sectors to join. Therefore, the key flows, key sectors and key communities should receive more attention when making energy-related policies.

Soil organic carbon (SOC) and inorganic carbon (SIC) are important carbon reservoirs in terrestrial ecosystems. A large portion of carbon from stover enters the atmosphere after stover return. Howe...

Organic amendment can increase soil zinc (Zn) availability and its uptake in cereals. Conversely, Zn transformation in soil may modify soil organic carbon (SOC) dynamics. To date, the effects of the simultaneous addition of organic material and Zn fertilizer on soil SOC storage and crop Zn enrichment have received little attention. Here, with a view to clarifying this problem, a 2-year wheat-based field study was conducted on the Loess Plateau in China with the following treatments: control, SR alone (SR7.5, 7.5 Mg·ha−1), ZF alone (ZF15, 15 kg Zn·ha−1), and SR plus ZF (ZF15SR7.5). The results indicate that loss of SOC after 2 years was 0.6 Mg·ha−1 in the control soil, and an input of 2.2 Mg C·ha−1·y−1 was needed to maintain the pre-experimental SOC stock. However, the increase in SOC storage after 2 years was 1.0 Mg·ha−1 in soil with SR7.5 and 2.6 Mg·ha−1 in soil with ZF15SR7.5, which accounted for 9.3% and 24% of residue-C input, respectively. On the other hand, the concentration of available Zn in soil with ZF15 was 3-fold higher than that in the control soil, but lower than that in soil with ZF15SR7.5 in both years. The Zn uptake by wheat and the grain Zn concentration also increased as the soil Zn availability increased, especially in the second year. Most importantly, in soil with ZF15SR7.5, the wheat grain Zn concentration reached 38 mg·kg−1 after 2 years, and the estimated dietary-absorbed Zn was 3.65 mg·d−1, which met the recommended Zn intake of 3 mg·d−1 for adults. Therefore, combining SR and ZF shows a promising synergistic effect for the enhancement of both SOC storage and wheat grain Zn bioavailability on China’s Loess Plateau and other drylands.

Straw return is a widely recognized strategy for increasing soil organic carbon (SOC) sequestration and improving soil quality and crop productivity. A 4-year-long field experiment established in 2008 was conducted to investigate the effects of the combined return of maize and wheat straw on the SOC stock at a soil depth of 0–20 cm in an intensive summer maize (Zea mays L.)–winter wheat (Triticum aestivum L.) cropping system in the Guanzhong Plain. The study involved four treatments with four replicates: low return of maize and wheat straw (ML–WL), low return of maize straw and high return of wheat straw (ML–WH), high return of maize straw and low return of wheat straw (MH–WL), and high return of maize and wheat straw (MH–WH). Compared with the SOC stock in the pre-experimental soil, the SOC stock in the 0–20 cm soil layer decreased by 2.6% under the ML–WL treatment, and in contrast, increased by 1.9% in ML–WH and 14.4% in MH–WH. Similarly, the stabilization rate gradually increased from 2.4% in ML–WH to 10.0% in MH–WH, though an obvious decrease of 6.8% was found in the ML–WL treatment. A significant linear relationship (P

Potassium (K) input is essential for the improvement of soil fertility in agricultural systems. However, organic amendment may differ from mineral K fertilization with respect to modifying the soil K transformation among different fractions, affecting soil K availability. We conducted a 60-day lab incubation experiment to evaluate the response of soil K dynamics and availability in various fractions with a view to simulating crop residue return and chemical K fertilization in an Anthrosol of northwest China. The tested soil was divided into two main groups, no K fertilization (K0) and K fertilization (K1), each of which was subjected to four straw addition regimes: no straw addition (Control), wheat straw addition (WS), maize straw addition (MS), and both wheat straw and maize straw addition (WS+MS). Soil K levels in the available (AK) and non-exchangeable (NEK) fractions were both significantly increased after K addition, following the order of K>WS>MS. Fertilizer K was the most efficient K source, demonstrating a 72.9% efficiency in increasing soil AK, while wheat and maize straw exhibited efficiencies of 47.1% and 39.3%, respectively. Furthermore, K fertilization and wheat and maize straw addition increased the soil AK in a cumulative manner when used in combination. The mobility factor (MF) and reduced partition index (IR) of soil K were used to quantitate the comprehensive soil K mobility and stability, respectively. Positive relationships were observed between the MF and all relatively available fractions of soil K, whereas the IR value of soil K correlated negatively with both MF and all available fractions of soil K. In conclusion, straw amendment could be inferior to mineral K fertilization in improving soil K availability when they were almost equal in the net K input. Crop straw return coupled with K fertilization can be a promising strategy for improving both soil K availability and cycling in soil–plant systems.